460 BIOLOGICAL EFFECTS OF RADIATION 



energy absorbed per unit volume of tissue. When equal amounts are 

 absorbed in equal volumes, the effects are the same, regardless of the 

 different penetrating powers of the rays. 



Not only do all wave-lengths of radiation, and also the beta rays of 

 radium, produce the same histological effects, but they also elicit the same 

 more delicate changes in the cell constituents. Fuhs and Politzer (10) 

 find that the morphological changes in the chromosomes and the order in 

 which they make their appearance are alike, whether X- or gamma rays 

 are the exciting agents. Politzer and Pauli (31), however, reported that 

 after exposure to cathode rays, whose intensity is very great, the cells 

 during mitosis display abnormalities in the achromatic figure not seen 

 after treatment with X-rays. They therefore concluded that these rays 

 produce a specific effect. But more recently it has been demonstrated 

 that these same characteristics can be produced by X-rays if the latter 

 are delivered at the rate of 40,000 r per min., an intensity comparable with 

 that of the cathode rays (11). It has also been claimed that mono- 

 chromatic radiations of different wave-lengths have the same effect on 

 tissue culture cells, but mixed radiation produces a different kind of 

 reaction which expresses itself in the changed mode of growth of the 

 culture (39). The evidence on this point is not convincing. 



Other experiments in which the criterion of effect is not a visible 

 morphological change but rather a physiological or genetic alteration 

 also show that the quality of radiation does not determine the nature of 

 the effect. Hoffmann (19) finds that the reaction of the protozoan 

 Opalina to vital dyes is the same for various X-ray wave-lengths : Feicht- 

 inger (6) has shown that the viscosity changes induced in Spirogyra by 

 alpha and beta rays are essentially the same when equal energy per unit 

 volume is absorbed. Finally, Hanson and Heys (15) first noted that 

 gamma rays and X-rays produce the same mutations in Drosophila. 

 The results of subsequent genetic experiments with radiations are 

 reviewed by Timofeef-Ressovsky (38). 



The statement is often made that qualitative differences in the 

 effectiveness of different wave-lengths are shown by the elective proper- 

 ties of the rays, a term used to describe the well-known fact that hard, 

 highly filtered radiations may, under appropriate conditions of dosage, 

 injure certain tissues while leaving others unharmed. When the testis 

 is exposed to gamma rays of low intensity, the seminal epithelium alone 

 is injured; but if X-rays of much higher intensity are used, the entire 

 organ undergoes massive degeneration (33). Observations of this kind 

 gave rise to the belief that gamma rays, because of their short wave- 

 length, could produce better therapeutic results than were possible with 

 X-ray treatment. There was much clinical evidence to support this 

 view. But more recent work has shown conclusively that the favorable 

 clinical effects following the use of radium are not due to any specific 



